Jesus turns to his disciples and gives them the lesson that it's hard for the rich to enter the kingdom because their worth is bound up in their possessions. A person might have the perfect spiritual resume, but until they are willing to be generous toward others, both physically and spiritually, then they will be outside the kingdom of heaven.
This troubles the disciples, who like many people in their day believed that wealth was a sign of God's blessing. Peter then pipes up with the obvious question, "Look, we have left everything and followed you. What then will we have?" Jesus assures him and the others that their dispossession of family, job, wealth and status won't go unrewarded. In order to be first in God's world, you have to be willing to be last.